Understanding the apparent fractional charge of protons in the aqueous electrochemical double layer

Leanne D. Chen, Michal Bajdich, J. Mark P. Martirez, Caroline M. Krauter, Joseph A. Gauthier, Emily Ann Carter, Alan C. Luntz, Karen Chan, Jens K. Nørskov

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17 Scopus citations

Abstract

A detailed atomic-scale description of the electrochemical interface is essential to the understanding of electrochemical energy transformations. In this work, we investigate the charge of solvated protons at the Pt(111) | H2O and Al(111) | H2O interfaces. Using semi-local density-functional theory as well as hybrid functionals and embedded correlated wavefunction methods as higher-level benchmarks, we show that the effective charge of a solvated proton in the electrochemical double layer or outer Helmholtz plane at all levels of theory is fractional, when the solvated proton and solvent band edges are aligned correctly with the Fermi level of the metal (EF). The observed fractional charge in the absence of frontier band misalignment arises from a significant overlap between the proton and the electron density from the metal surface, and results in an energetic difference between protons in bulk solution and those in the outer Helmholtz plane.

Original languageEnglish (US)
Article number3202
JournalNature communications
Volume9
Issue number1
DOIs
StatePublished - Dec 1 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)

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    Chen, L. D., Bajdich, M., Martirez, J. M. P., Krauter, C. M., Gauthier, J. A., Carter, E. A., Luntz, A. C., Chan, K., & Nørskov, J. K. (2018). Understanding the apparent fractional charge of protons in the aqueous electrochemical double layer. Nature communications, 9(1), [3202]. https://doi.org/10.1038/s41467-018-05511-y